The present disclosure relates generally to the testing of integrated circuits (ICs), and more particularly to an improved failure analysis (FA) technique for evaluating interconnect system failures in semiconductor devices and/or packaged assemblies.
Time Domain Reflectometry (TDR) is a well known technique of characterizing an electrical path by sending a pulse of energy such as a voltage step signal into the electrical path and monitoring reflections that are returned or reflected back from an endpoint of the electrical path. The TDR based instrument essentially works on the same principle as radar and uses a stimulus/echo technique to determine the length of the electrical path. The TDR instrument measures the time it takes for the input signal to travel down the electrical path, encounter an end point, and reflect back. The TDR instrument then converts this time to distance and typically displays the information as a waveform and/or distance reading. TDR has traditionally been used to evaluate and test the integrity of all types of interconnect systems such as transmission lines, power lines, telephone, cable TV, optical fibers, and the like.
The TDR concept is presently being used for analyzing and testing interconnections and signal paths on all types of electronic circuitry including semiconductor circuitry, semiconductor devices and integrated circuit (IC) chips. The electronic circuitry being tested, e.g., test samples, may include partially and/or fully assembled semiconductor devices. The use of the TDR technique as a FA tool is described in further detail in the following United States patent and technical paper, which are hereby incorporated herein by reference into this specification: 1) U.S. Pat. No. 6,798,212, entitled “Time Domain Reflectometer Probe Having A Built-In Reference Ground Point”, Stierman, et al., and 2) “Comparative Time Domain Reflectometry (TDR) Analysis As A Packaging FA Tool”, Charles Odegard and Craig Lambert, ISTFA '99, The 25th International Symposium for Testing and Failure Analysis, 14–18 Nov. 1999, Santa Clara, Calif., (Copyrighted Paper). However, analyzing and interpreting waveforms and/or test results obtained from traditional and/or legacy TDR test systems for locating a point of failure may be difficult, subjective and time consuming since the traditional TDR technique typically lacks the high resolution and may show a broadened reflection pattern around the failure point such as an open or short circuit. Thus, many FA tools used in interconnect testing are often unable to identify an exact position where the failure has occurred.